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Bings and EGTs

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larry(at)macsmachine.com
Guest

Posted: Thu Feb 23, 2006 1:01 pm Post subject: Bings and EGTs

Hi guys,

I went flying yesterday and noticed something that was interesting for 

those of us

with Bing carbs.  The EGTs climbed to their normal 1420 at high climb 

4800 rpm

and the higher I got (4500 ft), the more the EGTs drifted lower.  It 

eventually permitted

a high rpm without going above the 1400 deg f.  Nice for a good 

cross-country

cruise, but as I descended to land, EGTs climbed back up to set limits 

on my EIS and the

rpms had to be reduced to keep the EGTs at or below limits.  Not something

I'm worried about, but it seemed strange to see EGTs behind the curve 

while descending.

On final everything was well below limits, but I was wondering about the 

altitude compensating

carbs and if they ever get out of whack or is this normal.  Does this 

square with anyone else's

experience?



Larry McFarland - 601HDS at 85 hours and still testing.

frank.hinde(at)hp.com
Guest

Posted: Thu Feb 23, 2006 2:06 pm Post subject: Bings and EGTs

Hmm, Can't say I have noticed this Larry, probably because I have never

looked at the EGT guage except to wonder how a valve could stand all

that heat...



Frank



Do not archive 



--

larry(at)macsmachine.com
Guest

Posted: Thu Feb 23, 2006 3:01 pm Post subject: Bings and EGTs

Frank,

The cylinder head temps never get above 195, so I doubt the EGTs are a 

problem at 1450 (my set limit).

The aluminum heads at the exhaust are what I'd be worried about, but 

those temps have been o.k. I can fly

wide open at 4500 feet or so and hold 130 mph, but it seems weird to 

watch the EGTs climb from below

1400 as I was letting off and descending.  I can't figure out why. 

Ambient temps were in the high 30s,

really cool clear air. It would seem the carbs are still richer at 

altitude and become lean during descent.

This would seem to be a reverse of what I'd expect.



Larry

do not archive



Hinde, Frank George (Corvallis) wrote:



 	  Quote: 	
		  



Hmm, Can't say I have noticed this Larry, probably because I have never

looked at the EGT guage except to wonder how a valve could stand all

that heat...



Frank



Do not archive 

Subject: Bings and EGTs




--> <larry(at)macsmachine.com>



 EGTs climbed back up to set limits on my EIS and the

rpms had to be reduced to keep the EGTs at or below limits.  Not

something I'm worried about, but it seemed strange to see EGTs behind

the curve while descending.

On final everything was well below limits, but I was wondering about the

altitude compensating carbs and if they ever get out of whack or is this

normal.  Does this square with anyone else's experience?



Larry McFarland - 601HDS at 85 hours and still testing.

d3dw(at)msn.com
Guest

Posted: Thu Feb 23, 2006 5:26 pm Post subject: Bings and EGTs

Larry,

   It seems that if you put your nose down to descend from an established cruise without pulling back, then your rpm has to increase...more heat? don

  ---

larry(at)macsmachine.com
Guest

Posted: Thu Feb 23, 2006 6:15 pm Post subject: Bings and EGTs

Don Walker wrote:



 	  Quote: 	
		  



  



  No Don,
	


  I reduce throttle to lose altitude, do tip the nose down a bit, but 

found the reduction a little short of what was needed

to keep EGTs from climbing.  Coming off 4800 to about 4300 rpm and 

descending out of 4500 feet found EGTs

rising to the set limit until 4000 rpm and then backed down well after 

cutting rpms to 3000 entering final approach.

Never noticed this from a high of only 3500 feet, but from 4500 ft, it's 

curious why EGTs would rise on descent.

Maybe the difference of a 50 degree rise is just delayed cooling or heat 

not flowing as fast out the pipes at a slight

reduction of rpm on a descent approach.



Larry

do not archive



 	  Quote: 	
		  Larry,

   It seems that if you put your nose down to descend from an established cruise without pulling back, then your rpm has to increase...more heat? don

  Hi guys,

  I went flying yesterday and noticed something that was interesting for

  those of us with Bing carbs.  The EGTs climbed to their normal 1420 at

  high climb 4800 rpm and the higher I got (4500 ft), the more the EGTs

  drifted lower.  It eventually permitted a high rpm without going above

  the 1400 deg f.  Nice for a good cross-country cruise, but as I

  descended to land, EGTs climbed back up to set limits on my EIS and the

  rpms had to be reduced to keep the EGTs at or below limits.  Not

  something I'm worried about, but it seemed strange to see EGTs behind

  the curve while descending.

  On final everything was well below limits, but I was wondering about the

  altitude compensating carbs and if they ever get out of whack or is this

  normal.  Does this square with anyone else's experience?



  Larry McFarland - 601HDS at 85 hours and still testing.

d3dw(at)msn.com
Guest

Posted: Thu Feb 23, 2006 6:57 pm Post subject: Bings and EGTs

In that case your apparent wind may have something to do with it, which affects cowl pressure and air flow. do you suppose you are maintaining a constant cowl pressure though the descent?

  ---

larry(at)macsmachine.com
Guest

Posted: Fri Feb 24, 2006 7:07 am Post subject: Bings and EGTs

Don,

I guess the cowl air flow would be reduced on descent and that might 

allow more heat to accrue at the sensor. I was

thinking the altitude compensation built into the carbs was getting 

behind on enrichment. It could be either for the sake

of only 50-60 degrees.



Larry

do not archive



Don Walker wrote:



 	  Quote: 	
		  



In that case your apparent wind may have something to do with it, which affects cowl pressure and air flow. do you suppose you are maintaining a constant cowl pressure though the descent?



  Don Walker wrote:



     No Don,

    I reduce throttle to lose altitude, do tip the nose down a bit, but

  found the reduction a little short of what was needed

  to keep EGTs from climbing.  

  Maybe the difference of a 50 degree rise is just delayed cooling or heat

  not flowing as fast out the pipes at a slight

  reduction of rpm on a descent approach.



  Larry

  do not archive



  >Larry,

  >   It seems that if you put your nose down to descend from an established cruise without pulling back, then your rpm has to increase...more heat? don

  >

  >

   Nice for a good cross-country cruise, but as I

  >  descended to land, EGTs climbed back up to set limits on my EIS and the

  >  rpms had to be reduced to keep the EGTs at or below limits.  Not

  >  something I'm worried about, but it seemed strange to see EGTs behind

  >  the curve while descending.

 

  >  Larry McFarland - 601HDS at 85 hours and still testing.

  >

d3dw(at)msn.com
Guest

Posted: Fri Feb 24, 2006 8:36 am Post subject: Bings and EGTs

I dunno, just brainstorming with you. Looks like increased speed would increase cowl pressure to affect the mixture...and vice versa. Rate of descent may have something to do with it, too. I assume you are letting down at three to five hundred fpm? 

    I am glad you are noting these things, Larry, Helps us all.  don

  ---

garyk2(at)cox.net
Guest

Posted: Fri Feb 24, 2006 9:35 am Post subject: Bings and EGTs

 	  Quote: 	
		   really cool clear air. It would seem the carbs are still richer at

 altitude and become lean during descent.

 This would seem to be a reverse of what I'd expect.


	


I agree Larry - they should get richer with descent, and maybe they are.  I

just read something that mentioned higher EGT with richer mixture because it 

is still burning when it's coming out of the exhaust (just found the 

article - Sport Aviation feb 06 p101).



Sorry I can't help - no EGT's yet.  I'm still trying to get my homemade 

engine monitor working.  Right now I'm flying dumb and happy with just the 

basic temps and pressure.  I'm sure I'll have lot's of questions when I'm 

monitoring and recording everything.



gary

larry(at)macsmachine.com
Guest

Posted: Fri Feb 24, 2006 9:42 am Post subject: Bings and EGTs

Don,

I spoke with technical support person at Bing and he said that on 

descent, sometimes cowl pressure under lowering throttle settings

are still enough to lean out the mixture a bit and temps will go up.  

You were right.  He also said that the enrichment (choke)

cable could be pulled during the descent while rpms are reduced from 

4500 rpm to 3500 rpm and the EGTs should return to normal.

I'll have to try that on the next trip out.

Larry McFarland - 601HDS

Don Walker wrote:

 	  Quote: 	

I dunno, just brainstorming with you. Looks like increased speed would increase cowl pressure to affect the mixture...and vice versa. Rate of descent may have something to do with it, too. I assume you are letting down at three to five hundred fpm? 

    I am glad you are noting these things, Larry, Helps us all.  don

  Don,

  I guess the cowl air flow would be reduced on descent and that might

  allow more heat to accrue at the sensor. I was

  thinking the altitude compensation built into the carbs was getting

  behind on enrichment. It could be either for the sake

  of only 50-60 degrees.

  Larry

  Don Walker wrote:

  >

  >

  >In that case your apparent wind may have something to do with it, which affects cowl pressure and air flow. do you suppose you are maintaining a constant cowl pressure though the descent?

  >

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